Hello Shootist,
I can't say which type of wire the Nautilus Heads use, but there are 2 basic types... Kanthal and NiChrome. For the same diameter, NiChrome has less Ohms/inch than Kanthal. The majority of Heads you'll find (those form China) are using NiChrome. When most Americans do a rebuild, they are using Kanthal.
Approximately 0.91 Ohms/inch for 31 AWG Kanthal A1 (Mfg Spec) <----- Kanthal A1 is recommended for higher heat capacity
Approximately 0.87 Ohms/inch for 31 AWG Kanthal A
x(Mfg Spec)
Approximately 0.85 Ohms/inch for 31 AWG Kanthal D
x(Mfg Spec)
Approximately 0.73 Ohms/inch for 31 AWG NiChrome 60 (Calculated)
Approximately 0.69 Ohms/inch for 31 AWG NiChrome 80 (Calculated)
So it depends on the type of wire that is originally in the Aspire Nautilus Heads.
You may also find this helpful . . .
Approximately 0.46 Ohms/inch for 28 AWG Kanthal A1
Approximately 0.57 Ohms/inch for 29 AWG Kanthal A1
Approximately 0.72 Ohms/inch for 33 AWG Kanthal A1
Approximately 0.91 Ohms/inch for 31 AWG Kanthal A1
Approximately 1.15 Ohms/inch for 32 AWG Kanthal A1
Approximately 1.45 Ohms/inch for 33 AWG Kanthal A1
Approximately 1.84 Ohms/inch for 34 AWG Kanthal A1
I have seen variations for these Ohms/inch numbers, so the actual Ohms/inch may depend on the Manufacturer, but they are close.
It has been mentioned that the diameter of the coil comes into play. The wicking you wrap around may also effect that. For example, you may be wrapping around 2.5mm Silica, but your wraps will likely be a bit tight and the coils could have less than a 2.5mm inside diameter. The Calculators can be helpful, but they may not use the exact Ohms/inch of your wire, and can't take into account any lessening of diameter due to something like being wrapped tighter around Silica. They also may not take into account the lead length from the coils to the plus and minus terminations.
When rebuilding a Tank Head, what I do is wrap my coil (around wicking like Silica, or around a drill bit if for cotton), then mount it in the Head, but I
don't cut off the excess leads yet. I take an Ohm reading with an Ohmmeter. If I need another wrap, I can do it, and if I need to remove a wrap, I can do it. Once I know how many wraps I need, then I can duplicate the process. This applies to single coils and dual coils, or any number of coils.
Like Steve said, for a Dual Coil, you double the desired
Head Ohms of each separate Coil. Two 3.0Ω Coils in Parallel (Dual Coil) will yield a 1.5Ω Head, and so on. It's OK if they aren't precisely 3.0Ω (or what ever you need). Close is good enough for your desired goal.
Many rebuilders are not trying to rebuild the Aero Heads and other Dual Coil Heads with two coils. They are using Single Coils made with 28g Kanthal.
https://www.youtube.com/watch?v=XjXsAuRPH8Y
The Aero uses the same Heads as the ProTank 3, so you can Google that for rebuild techniques, but you can also follow any techniques for the ProTank 1 and 2. You just have to make sure that your wicking is fluffed up enough on the outside to cover and seal the gap on both sides where it exits the Head, so you don't get flooding into your battery. This is mentioned in the video above. He uses 28g for a single 1.4Ω coil. Depending on the Vamo version you have, it may need more Ohms than this, so just add another wrap if you follow the technique above. If you want to make Dual Coils in typical round coils (not like above), I'd say you'll need 32g or even 34g Kanthal A1.
Another thing I do, instead of using an online calculator, is straighten my Kanthal, leave some extra wire on one end for the lead that will exit the Head when the coil is wrapped, hold the wire on my desk with one Ohmmeter lead, and run the other meter lead along the wire to find the approximate point where my desired Ohms is. I put a bend at both places, and cut the wire with some extra on the end to be cut, so I'll have wire on both ends to exit the Head. Then I wrap that metered length around my wicking or drill bit. It comes out close, but my Multimeter isn't real accurate on low Ohms. Get a good Multimeter that can Zero the Ohms scale when the leads are shorted together, and you should be able to do fine without an online calculator. Then, something like this can be very handy . . .
The Omnitester
One last note. Some manufacturers are making Heads of this type with Ribbon Wire now. I recently rebuilt a ProTank 2 Head with 0.5 x 0.1 Kanthal A1 Ribbon Wire, wrapped around two strands of 2.5mm Silica. A 4/3 wrap on this came in at 1.7Ω to 1.8Ω (for me). Ribbon Wire will last longer in this type of Head than the smaller gauge Round Wire they use, and it works great. You may want to consider giving this a try. The smallest I've seen in the States is 0.4 x 0.1 Kanthal A1 Ribbon Wire.
0.4mm x 0.1mm
x11.4Ω/ft
xx0.95Ω/inch
0.5mm x 0.1mm
xx9.2Ω/ft
xx0.76Ω/inch
I hope this helps.
